Manchester Conditioning Update 10

It’s getting ugly

I had 16 oysters die today from various treatments. Based on Steven’s suggestion on Monday, I moved the oyster bags to individual 5 gallon buckets on Laura’s larval heated line, around 18 ºC. When I opened oysters that were dead, they all looked really ripe, and there were no signs of any disease. My guess is there’s something in the combination of the kiddie pool and high temperature that’s getting to them.

Table 1. Revised oyster counts in each tank, as of July 25.

Tag Label

A

B

Total

1

3

7

10

2

5

8

13

3

2

6

8

4

2

7

9

5

6

8

14

6

4

8

12

Heat Shock

3

4

7

Full Amb

0

6

6

Spare

1

3

4

Total

26

57

83

I cut open the ones that were dead and with the exception of two, preserved them for future testing. Three oysters were stored in falcon tubes with ethanol, three in the freezer and a jar with about six oysters was put in the fridge. Not entirely sure what to do with them yet, but at least I have them. The ones that were died were quite ripe and did not look unhealthy.

Figures 1-4. Examples of oysters that died.

Oysters in Figures 1-4 were also sexed. All were male.

Figures 5-8. Microscope images of male gametes.

Other things I did today:

Turned off immersion heaters

Cleaned algae header and filled with 1.6 L Reed’s paste

Removed lines from oyster tanks and bleached algal line

Counted about 30 2 gallon buckets that can be used for fertilization

Set up buckets for each bag of oysters with 26 L/hr drippers and airstones

Temperature is now around 18ºC instead of 23ºC. I talked to Rhonda and she’s a bit concerned that the oysters may start to reabsorb their gametes. She once had to drop broodstock to 15ºC two days before a spawn and it was fine. Maybe this will also be okay? Can they really reabsorb that quickly?

Oysters are being fed live algae

I will be back Thursday to check on oysters and continue preparing for spawn. I’m really hoping that no more die — I think we’ve eliminated all possible stresses! All I need is for them to be alive until I spawn them.